It’s been nearly three years since Chicago police Officer Thomas Wortham IV was shot and killed with a gun purchased in Mississippi by a straw purchaser -- a person who buys guns for those who aren't allowed to.

But on Friday, his sister Sandra Wortham praised proposed legislation that some lawmakers say would bring more stringent penalties for people continuing the practice throughout the country.

The gun-trafficking bill, co-sponsored by U.S. Sen. Mark Kirk, R-Ill., and U.S. Sen. Dick Durbin, D-Ill., would make it a felony to buy a gun from a federally licensed dealer on behalf of any other person, or to buy a gun from a private seller on behalf of someone who is not eligible to own one.

“Legislation like this prevents them from being able to claim ignorance, right? In (my brother’s) case, according to the (news) reports I’ve read, the individuals said, ‘Well, I didn’t realize what I was doing.’ So now they can’t say that,” Sandra Wortham said at a news conference at Chicago police headquarters, flanked by police Superintendent Garry McCarthy and Durbin.

“So now, yes, we’re saying to people if you choose to buy a weapon then give it to someone else, you’re going to be held accountable for that and we’re going to make you pay,” Wortham continued.

Sen. Chuck Grassley of Iowa, the top Republican on the panel, was the only member of his party to vote in favor. Kirk and fellow Republican co-sponsor Susan Collins of Maine weren't able to vote, as neither is on the panel. The bill still has to pass through the House and Senate.

A section of the bill was named after Hadiya Pendleton, a Chicago teen who was slain in January about a week after attending the second inauguration for President Barack Obama.

The bill is also the first piece of firearms legislation to make its way to the full Senate since the deadly December shootings in Newtown, Conn., which killed 20 first-graders and six adults.

Law enforcement has complained for years that straw buyers undermine local laws. Nowhere is the problem more apparent than Chicago, where there is no shortage of illicit guns despite onerous regulations and a ban on gun shops.

It is illegal to make false statements in connection with the purchase of a firearm, but a straw purchaser who is caught doing so will typically face nothing more than a so-called paperwork violation, for which the penalties are low.

The new legislation would call for penalties as severe as 15 years in prison.

“For straw purchasers, for those who are going to buy guns and turn them over to the thugs and criminals, get ready. When this bill becomes law, you’re going to deal with a hard time federal crime. Let the word on the street get out,” Durbin said at the news conference. “Girlfriends, think twice. Is it worth 15 years in prison to buy that gun and to go and sell it to some gangbanger or some boyfriend who is going to use it to commit a crime?”

Also at the news conference, Cleopatra Cowley-Pendleton, Hadiya’s mother, expressed her gratitude for the legislation being brought to Congress.

“If there were laws like the one’s that’s been proposed it’s quite possible that my baby wouldn’t have to be part of a bill such as this,” she said.